Match features (ORB)

POST /api/image-match-features3 quota units per call · cache hits free

Detect and match feature points between two images. Robust to rotation, scale, and modest lighting changes. Useful for image alignment and panorama stitching.

Detects feature points in two images and finds correspondences between them. The matching is robust to rotation, scale, and modest lighting differences — much more flexible than pixel- level template matching. Useful for image alignment, panorama stitching, motion estimation, and object-pose estimation. Returns each matched pair as `{(x1, y1), (x2, y2), distance}` where distance is the descriptor similarity.

Inputs

Name	Type	Default	Description
image*	file	—	Query image bytes.
target*	file	—	Train image bytes — the second image to match against.
nfeatures	number (50…8000)	1000	Max ORB keypoints per image.
maxMatches	number (1…1000)	50	Cap on returned match pairs.

Response

Modes: json. Cache: yes (24h TTL).

Every response carries x-cache (HIT / MISS / BYPASS), x-cache-signature (stable across identical inputs), and the rate-limit headers listed below.

Quota & limits

Cost per call	3 units against the 10,000-unit monthly quota. Cache hits are free — only cache misses decrement.
Burst limit	200 requests per rolling minute, shared across all tools.
Max request size	`50 MiB` (base64 inflates file payloads ~33% — the limit applies to the decoded bytes).
Max response size	`1 MiB`
Timeout	30s wall clock.
Rate-limit headers	`X-RateLimit-Limit`, `X-RateLimit-Remaining`, `X-RateLimit-Burst-Limit` on every response; `X-Quota-Warning` once 80% of the monthly quota is spent; `Retry-After` on 429s.

Errors

Errors are JSON with an error string; schema failures add a details object (Zod's flattened field errors).

Status	When	Body
400	Input fails the tool's schema (wrong type, missing required field, malformed base64) or the file bytes can't be parsed as the expected format.	{ "error": "invalid inputs", "details": { "fieldErrors": { … } } }
401	Missing or invalid X-Api-Key / X-Account-Id headers (or no session when called from the browser).	{ "error": "unauthorized" }
404	Unknown tool id, or calling /api/* on the website hostname instead of api.xtract.bot.	{ "error": "not found" }
413	Request body over the tool's max request size, or an image header declaring more megapixels than the tool's pixel budget.	{ "error": "…exceeds maxRequestBytes…" }
415	Content-Type isn't application/json on the json-body transport.	{ "error": "unsupported content-type; expected application/json" }
429	Monthly quota or the 200/min burst limit exhausted. Check Retry-After and the X-RateLimit-* headers.	{ "error": "monthly quota exceeded", "monthRemaining": 0, … }
5xx	Conversion engine failure. Safe to retry; if it persists, the input is hitting a bug — please report it.	{ "error": "…" }

Code samples

Built from the self-match example.

# Download or substitute the example input:
#   curl -O https://xtract.bot/examples/image-align/sample.png
IMAGE=$(base64 -w0 < sample.png)
# Download or substitute the example input:
#   curl -O https://xtract.bot/examples/image-align/sample.png
TARGET=$(base64 -w0 < sample.png)

curl -X POST https://api.xtract.bot/api/image-match-features \
  -H "Content-Type: application/json" \
  -H "Accept: application/json" \
  -H "X-Account-Id: $XTRACT_ACCOUNT_ID" \
  -H "X-Api-Key: $XTRACT_API_KEY" \
  -d '{
  "image": "'"$IMAGE"'",
  "target": "'"$TARGET"'"
}'